[Diagnosis and treatment of autoimmune hemolytic anemia: the role of B-1 cells in secondary AIHA].

Autoimmune hemolytic anemia (AIHA) is a rare disease with an unknown etiology. Although the diagnosis of a typical case is expected to be easy, the actual diagnosis is often challenging due to the diversity of conditions. Prednisolone treatment continues for a long period and causes several adverse events, including infection and osteoporosis. Therefore, a solid understanding of the pathophysiology, depending on the disease type, is necessary to avoid ineffective and unnecessary treatment and achieve a good outcome. Previously, we reported two studies concerning colorectal cancer that ectopically expresses band 3 erythrocyte membrane protein, leading to cancer-related anemia without bleeding through an immune response identical to or resembling AIHA. In this article, the methods of laboratory examination for the diagnosis of AIHA are summarized to serve as physicians' reference. Furthermore, points for conventional management and emerging treatments against specific targets are briefly described. In addition, due to the increasing knowledge on B-1 cells' participation in malignant and autoimmune diseases, the pathophysiological role of B-1 cells in AIHA is scrutinized through their physiological function in innate and adaptive immunity, in terms of the production of anti-band 3 antibodies. The screening and analysis of primary disease in AIHA should improve clinical outcomes.